3 栈

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#!usr/bin/env python
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# encoding:utf-8
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class Stack:
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    def __init__(self):
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        self.stack = []  # 栈列表
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        self.size = 20  # 栈大小
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        self.top = -1  # 栈顶位置
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    # 元素进栈
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    def push(self, element):
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        if self.isFull():  # 如果栈满，引发异常
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            raise StackException('Stack is full')
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        else:
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            self.stack.append(element)
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            self.top += 1
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    # 元素出栈
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    def pop(self):
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        if self.isEmpty():  # 如果栈为空，则引发异常
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            raise StackException('Stack is empty')
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        else:
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            element = self.stack[-1]
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            self.top -= 1
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            del self.stack[-1]
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            return element
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    # 获取栈顶位置
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    def getTop(self):
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        return self.top
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    # 清空栈
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    def empty(self):
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        self.stack = []
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        self.top = -1
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    # 判断是否为空栈
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    def isEmpty(self):
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        if self.top == -1:
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            return True
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        else:
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            return False
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    # 是否为满栈
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    def isFull(self):
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        if self.top == self.size - 1:
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            return True
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        else:
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            return False
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class StackException(Exception):  # 自定义异常类
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    def __init__(self, data):
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        self.data = data
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    def __str__(self):
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        return self.data
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'''
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主函数
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'''
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if __name__ == '__main__':
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    stack = Stack()  # 创建栈
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    for i in range(10):
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        stack.push(i)  # 元素进栈
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    print('栈顶位置：', stack.getTop())
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    while not stack.isEmpty():
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        print(stack.pop())  # 元素出栈
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    stack.empty()  # 清空栈
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    for i in range(21):
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        stack.push(i)  # 引发异常